KIMURA and SAKAGAWA: SCALE PATTERNS OF PACIFIC SARDINE 



FiGUKE 5. — Growth in weight of Pacific sar- 

 dines reared in the laboratory for 24 months. 

 Mean weight is represented by a circle, and 

 one standard deviation is shown on each 

 side of the mean. The sample size is also 

 indicated. 



their fish was not known, we compared their data 

 for the 1937 and 1938 year classes with ours 

 (Figure 6). The results indicate that although 

 growth of the 1937 year class was fast, growth 

 was similar in fish caught in the 1930's and in 

 the laboratory-reared fish, 



Marr (1960) presented data on the average 

 length at time of first annulus formation (Li) 

 and showed that there was a sharp change in 

 Li to a higher level with the 1944 year class 

 landed at San Pedro. Using his data, we calcu- 

 lated separate estimates of average L\\ one for 

 the 1934-43 year classes, and another for the 

 1944-57 year classes. The estimates are 101.3 

 and 131.5 mm, respectively. Compared with our 

 estimate of 103.0 mm, growth of the 1934-43 year 

 classes was almost identical to that for the lab- 

 oratory fish, and growth for the 1944-57 year 

 classes appears to have been faster than that 

 for the laboratory fish. This faster growth may 

 be an artifact and is discussed in a later section. 



(a) 1937 YEAR CLASS ,^°s. J 





MAYJJflSONOJANFMAMJJASONDJANFMAM 

 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 



AGE (MONTH) 



Figure 6. — Comparison of growth of juvenile sardines 

 caught in the 1930's with growth of laboratory-reared 

 sardines. Data for the 1937 and 1938 year classes are 

 from Walford and Mosher (1943). 



BACK-CALCULATED LENGTHS 



Back-calculated lengths were computed for 

 two samples, taken in September (16th month) 

 and May (24th month). We reasoned that the 

 back-calculated lengths would give an independ- 



ent estimate of the time of mark formation, if 

 growth is assumed to follow that shown in Fig- 

 ure 4. The average back-calculated lengths based 

 on two methods are shown in Table 3. The first 

 method gave lower estimates than the second. 

 Both methods, however, gave back-calculated 

 lengths that were reasonably similar to average 

 lengths of samples collected during the period 

 when the marks formed. 



1049 



